[3D modeling in the field of morphology: methods, interest and results]

Evaluation of a temporal bone prototype by experts in otology

BACKGROUND

Inexperienced otologists require training on the temporal bone drilling process, prior to any surgical activity. The shortage of cadaveric temporal bones exerts pressure to create realistic physical prototypes. This paper describes the evaluation by otology experts of a specially developed temporal bone resin model.

METHODS

Computed tomography images were transformed into digital files, and anatomically identical right temporal bone models were created using stereolithography. These hand-painted resin prototypes were sent to 25 otologists, accompanied by a 20-item questionnaire.

RESULTS

Satisfaction rate was 92 per cent. The overall prototype score was 48.87 out of 60. Average scores were: 12.63 out of 15 for anatomy-morphology, 6.98 out of 9 for quality of drilling, 16.74 out of 21 for identification of anatomical elements and 7.41 out of 9 for stages of drilling. Limitations of the model included an excessively vivid facial nerve colour and difficulty in identifying the posterior semicircular canal. Disadvantages related to the thickness of the resin and its residues were identified.

CONCLUSION

The prototype appears to provide an attractive solution to the shortage of cadaveric temporal bones. However, interest in the model for drilling technique training for inexperienced otologists has not yet been assessed.

[Computerized three-dimensional reconstruction of the retrohepatic segment of inferior vena cava of a 20 mm human embryo]

The subdiaphragmatic venous drainage of the embryo is provided by the two caudal cardinal veins to which is added the subcardinal vein system, draining the mesonephros, the perispinal supracardinal veins and the umbilical and vitelline venous system. The anastomosis of certain segments of the embryonic venous structures and the disappearance of others are at the origin of the inferior vena cava. Since the 19th century, three-dimensional reconstruction of solid models from histological sections were developed. At present, the development of computerized three-dimensional reconstruction techniques allowed to operate a multitude of techniques of image processing and modeling in space. Three-dimensional reconstruction is a tool for teaching and research very useful in embryological studies because of the obvious difficulty of dissection and the necessity of introducing time as the fourth dimension in the study of organogenesis. This method represents a promising alternative compared to previous three-dimensional reconstruction techniques including Born technique. The aim of our work was to create a three-dimensional computer reconstruction of the retrohepatic segment of the inferior vena cava of a 20mm embryo from the embryo collection of Saints-Pères institute of anatomy (Paris Descartes university, Paris, France) to specify the path relative to the liver and initiate a series of computerized three-dimensional reconstruction that will follow the evolution of this segment of the inferior vena cava and this in a pedagogical and morphological research introducing the time as the fourth dimension.

Female pelvic autonomic neuroanatomy based on conventional macroscopic and computer-assisted anatomic dissections

PURPOSE

To confront nerve dissection, tissue staining, nerve immunolabelling and Computer-Assisted Anatomic Dissection (CAAD) in identifying the precise location and origin of intrapelvic autonomic nerve fibers and to provide a three-dimensional (3D) representation of their relationship to other anatomical structures.

METHODS

Serial transverse sections of the pelvic portion of five human female fetuses (18-31 weeks of gestation) were studied histologically (with hematoxylin/eosin and Masson trichrome) and immunohistochemically (anti-protein S100 antibody) digitized and reconstructed three-dimensionally with Surf driver software for Windows (Winsurf 4.3). Three fresh female adult cadavers were macroscopically dissected to individualize the inferior hypogastric plexus afferences and efferences and their anatomical relationships.

RESULTS

This combined investigation including the CAAD technique allowed identifying the precise location and distribution of the pelvic nerve elements and their relationships to female pelvic organs. Hypogastric nerves (HN) were located in the retrorectal multilaminar structure and joined the homolateral inferior hypogastric plexus (IHP) at the lateral border of the recto-uterine pouch. The intersection of the ureter with the posterior wall of the uterine artery precisely located the junction of HN and IHP. Antero-inferior branches supplying female sexual and continence organs originated from the antero-inferior angle of IHP and were bundled at the posterolateral vaginal wall.

CONCLUSIONS

CAAD is an encouraging anatomical method for the development of anatomical and surgical research and teaching. Complementary to traditional anatomical studies, it may provide useful anatomical data for the comprehension of postoperative sexual and urinary dysfunction and the development of nerve-sparing surgical techniques.

[Detection of cephalopelvic disproportion using a virtual reality model: a feasibility study of three cases]

Routine daily practice shows that successful vaginal delivery for women with suspected narrow pelvis or large fetus remains possible. We present a computer software for the detection of fetopelvic disproportion based on 3D vectorial reconstructions of the fetal head and maternal pelvis with simulation of head passage through the pelvis for collision detection. Three delivery simulations were generated from MR pelvimetry data in two patients, one with narrow pelvis and the other with macrosomic fetus. Based on the simulation, fetus size in both cases was appropriate for the pelvic size, but delivery simulation for the macrosomic fetus concluded that vaginal delivery was mechanically impossible. Further evaluation of this promising software on a larger patient population is necessary.

Coexistence of adrenergic and cholinergic nerves in the inferior hypogastric plexus: anatomical and immunohistochemical study with 3D reconstruction in human male fetus

Classic anatomical methods have failed to determine the precise location, origin and nature of nerve fibres in the inferior hypogastric plexus (IHP). The purpose of this study was to identify the location and nature (adrenergic and/or cholinergic) of IHP nerve fibres and to provide a three-dimensional (3D) representation of pelvic nerves and their relationship to other anatomical structures. Serial transverse sections of the pelvic portion of two human male fetuses (16 and 17 weeks' gestation) were studied histologically and immunohistochemically, digitized and reconstructed three-dimensionally. 3D reconstruction allowed a 'computer-assisted dissection', identifying the precise location and distribution of the pelvic nerve elements. Proximal (supra-levator) and distal (infra-levator) communications between the pudendal nerve and IHP were observed. By determining the nature of the nerve fibres using immunostaining, we were able to demonstrate that the hypogastric nerves and pelvic splanchnic nerves, which are classically considered purely sympathetic and parasympathetic, respectively, contain both adrenergic and cholinergic nerve fibres. The pelvic autonomic nervous system is more complex than previously thought, as adrenergic and cholinergic fibres were found to co-exist in both 'sympathetic' and 'parasympathetic' nerves. This study is the first step to a 3D cartography of neurotransmitter distribution which could help in the selection of molecules to be used in the treatment of incontinence, erectile dysfunction and ejaculatory disorders.

[3D reconstruction of anterior internal vertebral venous plexus of a human fetus: a feasibility study]

Anterior internal vertebral venous plexus have been studied extensively due to their clinical importance in diseases of the spine and obstruction of the inferior vena cava. The aim of this feasibility study was to reconstruct in 3D the lower thoracic area of the anterior epidural space of a 69 mm (crown-rump) human fetus from the Rouvière Collection, circa 1927. Forty slices (spaced by 40 microm) at the level of the tenth and eleventh thoracic vertebrae, and their lower adjacent intervertebral discs, were reconstructed in 3D using the commercial software SURFdriver. In a preliminary study, we had found that the structures of the epidural space are already formed at this stage of development, and that they are comparable to the adult stage (2002). Reconstruction of the microscopic slices in 3D allowed to better visualize spatially the structures of the venous plexus and their anatomical relationships. This technique could be used as a complement to the classically used histological studies.